Congestive heart failure (CHF) is a leading cause of death in the United States, and is the major cause of hospitalization in patients 65 years and older. CHF is also the single largest Medicare expenditure; accounting for approximately $4 billion annually. CHF occurs when the heart is unable to adequately supply enough blood to maintain a healthy physiological state. CHF may be treated by drug therapy, or by an ambulatory medical device (AMD) such as an implantable medical device (IMD).
Some IMDs may chronically stimulate excitable tissues or organs, such as a heart, to help restore or improve cardiac performance in a patient with CHF, or to treat abnormal cardiac rhythms. Such IMDs may have electrodes that may be positioned within the heart or on a surface of the heart. The electrodes may be electrically coupled to an electronics unit such as a pulse generator, such as via a lead, and may be used to deliver electrostimulation to the heart. One type of electrostimulation is cardiac resynchronization therapy (CRT) achieved by simultaneous or synchronized pacing of both left and right ventricles, which has been shown to be effective in improving cardiac function in some CHF patients with a depressed ejection fraction and dyssynchrony of inter- or intraventricular electromechanical activation.